This invention is directed to an improved engine having an external heat source and particularly to an engine which is driven by hot, pressurized liquid working fluid, such as water, which is volatilizable at the working temperatures and pressures.
Many attempts have been made to produce an engine which utilizes an external heat source to convert heat energy into useful work. The most notable external heat source engine designs utilizing vapor as the working fluid are the Rankine engine, the reciprocating steam engine, and the steam turbine. The Carnot engine, the Joule-Brayton engine and the Stirling engine are examples of external heat source engines utilizing gas as the working fluid. While these engine designs have been the subject of much theoretical considerations, they have not met with any significant commercial success other than the steam reciprocating engine and the steam turbine. The lack of commercial success has been due largely to the problem of providing small and efficient heat exhangers which facilitate the rapid and efficient heating of working fluid by an external heat source.
What has been needed and heretofore has been unavailable is an efficient energy conversion system which may be used with low grade heat sources. The present invention satisfies this need.